An alert system for volcanic emissionsusing satellite measurements

Nicolas THEYS

H. Brenot, J. van Gent and M. Van Roozendael (BIRA-IASB)

R. van der A (KNMI)

L. Clarisse, P.-F. Coheur, C. Clerbaux (ULB-LATMOS)

P. Valks, M. Rix (DLR)

2010 EUMETSAT Meteorological Satellite Conference

Córdoba, Spain, 20 – 24 September 2010

- Contents -

Ash plume from the Eyjafjallajokull eruption

on 15 Apr. 2010© Saeberg/Reuters

• Support to Aviation Control Service (SACS)

• Example of results for the

eruption of the Eyjafjallajokull volcano

• System and algorithmic developments

Background

• Volcanic eruptions may bring ash high up into the atmosphere where it poses a threat to aviation.

• The presence of sulphur dioxide (SO2) is often a tell-tale sign of possible volcanic activity.

• In the first day or two after an eruption SO2 and ash will travel together and therefore SO2 may serve as a marker for the ash.

Support to Aviation Control Service (SACS)

developed for ESA, within DUE (TEMIS) and GSE (PROMOTE) programmes

started in 2006, now extended for 3 years (SACS+)

The Support to Aviation Control Service (SACS) intends to deliver in near-real time data from space-based instruments regarding SO2 and aerosol (ash) data possibly related to volcanic activity. In case of an event notifications are send by email to users, pointing them to a dedicated web page with detailed information. If possible, information on the location, elevation and motion of volcanic plumes will also be provided, in collaboration with the SAVAA project.

Notifications of eventsand data from SACS+ can beuseful to the VAACs andother interested users: volcanic observatories, air quality monitoring institutes, scientist, etc.

Currently: 66 subscribers

Volcanic Ash Advisory Centres (VAACs)

Partners in SACS

Belgian Institute for Space Aeronomy (BIRA-IASB) leader

Royal Netherlands Meteorological Institute (KNMI)

Free University of Brussels (ULB)

German Aerospace Center (DLR) data provider

Data products of SACS

Instrument Data type Participants Data products Availability Alerts

SCIAMACHY

(ENVISAT)

UV/visible BIRA

KNMI

SO2 columns

absorbing aerosol index

+

+

+

GOME-2 (MetOp-A)

UV/visible DLR

KNMI

SO2 columns*absorbing aerosol index

+

+

[+]

OMI

(Aura)

UV/visible KNMI SO2 columns

absorbing aerosol index

+

+

[+]

IASI (MetOp-A)

Infrared ULB SO2 index and columns

ash indicator

[+]

[+]

[+]

Near-real time and archive service

+ = currently available [+] = to come during SACS+

* Operational product from DLR.

SACS portal (hosted by BIRA-IASB)

http://sacs.aeronomie.be/

Alert system: subscription to e-mail list

SO2 columns 06 May 2010SCIAMACHY OMI

GOME-2IASI

The eruption of the volcano Eyjafjallajokull

Aerosols

SCIAMACHY OMI

GOME-2

IASI

The eruption of the volcano Eyjafjallajokull

GOME-2Ash indicator

Alert system

.. currently only based on SCIAMACHY data

Eruption of the Vanuatu

Criteria for exceptional SO2 events

For each pixel with SO2 SCD>3 DU, the 8 surrounding pixels are evaluated:

-SO2 SCD>3 DU: + 1 point

-SO2 SCD<0 DU: -1 point

If ∑ points ≥ 5 then an alert is triggered

and an e-mail is sent to interested users

SACS notification of exceptional SO2 concentration ==================================================

Process date : 2005 05 15

Process time : 23:56:01

CET Instrument : SCIAMACHY

No. notices : 1

Alert notice : 1

-------------------- http://sacs.aeronomie.be/alert/?alert=20050515_224502_001

Start date : 2005 05 15

Start time : 22:45:02.724 UTC

Aver. long. : 167.7 deg.

Aver. latit. : -16.9 deg.

Aver. sza : 24.5 deg.

Max. SO2 vcd : 41.3 DU

Remark :

System development

night

09:30 am GOME-2, IASI

10:00 am SCIAMACHY

01:30 pm OMI, AIRS

IASI

day

SEVIRI (Europe)

AIRS

Development of an optimized SO2 alert system (multi-sensors approach).

MetOp-A

MetOp-A

Envisat

Aura

Aqua

Aqua

MSG

Objectives:

- increase the level of confidence of the alerts

- reduce the ∆t between the eruption and the time when the alert is sent.

Algorithmic developments

Slant column retrieval SO2 absorption along the mean light path

Backround correction for measurements at high SZA

Estimation of the vertical column by applying an air mass factor VCD=SCD/AMF

The SO2 vertical column is routinely retrieved from UV spectra using DOAS techniques:

(UV sounders)

Algorithmic developments

Tool

GODFIT: Direct fitting algorithm that includes LIDORT as forward radiative transfer model and a ‘state-of-the-art’ Rotational Raman Scattering (RRS) code.

Inversion capabilities

volcanic ash/aerosol retrieval based on the different light intensity and RRS response of absorbing/non absorbing aerosols.

improvement of the SO2 VCD retrieval (high SO2 signal).

retrieval of the peak altitude of the SO2 plume (particularly interesting for the VAACs).

Alternative approach: direct multi-wavelength fitting

Simultaneous SO2 column and plume height retrieval

Direct fitting applied to GOME-2

Poster 103 J. van

Gent et al.

Strong SO2 signal from Kasatochi (8 August 2008)

Weak SO2 signal from Eyjafjöll (9 May 2010)

(preliminary)

Summary

http://sacs.aeronomie.be/

• NRT delivery and archive of data and images of SO2 and aerosol/ash indexes from SCIAMACHY, OMI, GOME-2 and IASI (soon).

• E-mail notification of exceptional SO2 concentrations exists for SCIAMACHY.

• On-going development of an optimized SO2 alert system based on multi-sensors data (SCIAMACHY, OMI, GOME-2, IASI, AIRS, SEVIRI).

• Development of advanced retrieval algorithms to improve SO2 (e.g., height of the plume) and aerosol/ash satellite data products.